Resumo

SALAS-GARCIA, Javier; GARFIAS, Jaime; LLANOS, Hilario  e  MARTEL, Richard. Design and application of instruments for hydrometeorologic and hydrogeologic characterization. Bol. Soc. Geol. Mex [online]. 2010, vol.62, n.2, pp.233-247. ISSN 1405-3322.

Knowledge of the water cycle is an essential requirement to evaluate, plan and develop water resources. In this sense, this paper describes the principles of equipment operation, design, results of laboratory tests and the installation in the field offive devices: a rain gauge, an evaporimeter, a limnometer, a water table meter and a hygrometer. As the parameters measured vary with time, all the devices described are capable of storing and transmitting the data to a personal computer at programmable intervals. Moreover, the design enables the equipment to withstandfield conditions. As a result of the laboratory tests on the rain gauge, its maximum relative error is 4% for a daily rainfall of less than 500 mm/day. In addition, the method of evaporimeter measurement reduced by a factor of 5 the relative error in the pressure sensor used to measure the water level in an evaporation pan, resulting in a precision of 98.5%. A singular feature of both devices is the capability to self-calibrate after each duty cycle. Furthermore, the limnometer can measure the level ofsurface flow with a precision of 58 μm by the use of electromechanical positioning. In the case of the water table meter, it shows a full scale measurement error of 1.5%. As an additional advantage, this device measures the water table by determining differential instead ofabsolute pressure, thereby eliminating the need ofadditional equipment to compensate for the effect ofatmospheric pressure. Once the gypsum blocks used by the hygrometer are calibrated, it is possible to determine the relative humidity with a variation of 2.8% in the electrical resistance for a temperature range between 8°C and 17°C. In order to determine the possible effects of deterioration of the components, the field test took six months. After a series of design modifications, it was possible to construct the equipment in such a way that no corrective maintenance is required once it is installed. The most accurate of the five devices was the limnometer, which exhibited practically equal results in the laboratory andfield. As a result of the design optimization, the manufacturing cost of the five devices was 1250 dollars, which is about 12% of the cost of similar equipment.

Palavras-chave : instrumentation; rain gauge; evaporimeter; limnometer; water table meter; hygrometer.

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